ZCZC MIATCDEP2 ALL
TTAA00 KNHC DDHHMM
Tropical Storm Fernanda Discussion Number 4
NWS National Hurricane Center Miami FL EP072023
800 AM PDT Sun Aug 13 2023
The compact storm is currently exhibiting a CDO-type cloud pattern
with very cold embedded tops to near -80 deg C. Upper-level
outflow is well defined over the western semicircle of the
circulation. The current intensity estimate is set at 50 kt based
on a blend of subjective Dvorak estimates from TAFB and SAB along
with various objective estimates from UW-CIMSS.
Fernanda continues its west-northwestward trek, and the initial
motion estimate remains at around 285/9 kt. A weak mid-level ridge
is currently situated to the north of the system. Over the next
few days, the ridge is expected to strengthen somewhat. This
should result in a gradual increase in forward speed during the
forecast period with a turn toward the west in a few days. The
official forecast track is essentially an update of the previous one
and is very close to the dynamical model consensus, TVCE.
The tropical cyclone should continue to traverse sea surface
temperatures near 29 deg C for the next 36 hours or so with very
low vertical wind shear. Rapid intensification (RI) seems likely,
and the SHIPS RI indices show a significant likelihood of an
increase of intensity of around 30 kt during the next day or so.
The official forecast goes along with this guidance and calls for
Fernanda to become a hurricane in 12 hours or so, and to reach
category 2 strength within the next couple of days. By 48 hours and
beyond a drier air mass, seen in GOES-18 low-level water vapor
imagery to the west-northwest of the cyclone, should result in
weakening. The official forecast is near or a little below the
latest corrected consensus, HCCA, prediction.
FORECAST POSITIONS AND MAX WINDS
INIT 13/1500Z 15.4N 115.9W 50 KT 60 MPH
12H 14/0000Z 15.6N 117.2W 65 KT 75 MPH
24H 14/1200Z 16.0N 118.7W 80 KT 90 MPH
36H 15/0000Z 16.4N 120.4W 90 KT 105 MPH
48H 15/1200Z 16.9N 122.2W 90 KT 105 MPH
60H 16/0000Z 17.3N 124.3W 80 KT 90 MPH
72H 16/1200Z 17.5N 126.5W 70 KT 80 MPH
96H 17/1200Z 17.8N 132.0W 50 KT 60 MPH
120H 18/1200Z 18.0N 138.0W 35 KT 40 MPH
$$
Forecaster Pasch
NNNN